693 
FXUS65 KBOI 202215
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
315 PM MST FRI NOV 20 2009

.SHORT TERM...TONIGHT THROUGH SUNDAY...PRE-FRONTAL GUSTY EAST TO
SOUTH WINDS HAVE BEEN LOCALLY VERY WINDY IN THE MOUNTAIN HOME AREA
AND PARTS OF SOUTHERN HARNEY COUNTY TODAY. LOCAL BLOWING DUST WAS
OBSERVED AS WELL. WINDS ARE EXPECTED TO DECREASE TO 15-30 MPH
THROUGH THE LATE AFTERNOON THEN SHIFT TO THE SW AND NW 15-35 MPH
WITH THE COLD FRONTAL PASSAGE. THE FRONT APPEARED TO HAVE CROSSED
INTO THE LEE OF THE CASCADES IN WEST CENTRAL OREGON AS OF 2 PM AND
SHOULD REACH THE ORE-IDA BORDER 5-6 PM MST. PRECIP LOOKS TO LAG
THE FRONT BY 2-3 HOURS FOR A QUICK SHOT OF RAIN AND SNOW THIS
EVENING IN OREGON AND PRECIP CHANGING TO SNOW ABOVE 3000 FEET IN
IDAHO TONIGHT. VALLEYS LOOK TO DRY OUT SATURDAY MORNING AS SNOW
SHOWERS LINGER IN THE BAKER MOUNTAINS UNTIL NOON AND IDAHO
MOUNTAINS THROUGH MID-AFTERNOON. COLD AND DRY BUT CONSIDERABLE
CLOUDINESS AROUND SATURDAY NIGHT ALONG WITH ANOTHER ROUND OF GUSTY
SOUTHEAST TO SOUTH WINDS. NEAR NORMAL TEMPERATURES FOR LOWS
TONIGHT THROUGH HIGHS SUNDAY AFTER WARMING UP INTO THE 40S AND 50S
THIS AFTERNOON.

A STRONGER AND COLDER SYSTEM INTO SE OREGON LATE SATURDAY NIGHT
AND ACROSS IDAHO SUNDAY LOOKS TO BE A POTENTIAL WINTER STORM. WARM
ADVECTION AND MOISTURE WITH AROUND 120 PERCENT OF NORMAL PWS
QUICKLY TRANSITIONS TO COLD UNSTABLE CONDITIONS WITH WIDESPREAD SNOW
SHOWERS THROUGH THE AFTERNOON IN THE MOUNTAINS. UP TO A FOOT OF
NEW SNOW IS POSSIBLE SUNDAY IN THE WEST CENTRAL AND BOISE
MOUNTAINS ALONG WITH AREAS OF BLOWING AND DRIFTING SNOW. LAST TWO
RUNS OF THE NAM HAVE SHOWN 8-16 INCH SNOW ACCUMULATIONS SUNDAY
BUT THE GFS IS CLOSER TO 8-10 MAX AMOUNTS AND THE EC 4-7 INCHES
BASED ON QPF...SO THERE IS STILL SOME UNCERTAINTY IN THE
QPF/SNOWAMT. THE STORM TRACKS ARE SIMILAR SO A WX STORY HAS BEEN
ISSUED TO HIGHLIGHT THE POSSIBILITY OF A WINTER STORM SUNDAY
ACROSS THE NORTHERN MOUNTAINS. SNOW LEVELS WILL BE AT VALLEY
FLOORS IN THE MORNING AND AN INCH OR SO IS EXPECTED AT BOISE EARLY
SUNDAY MORNING.

.LONG TERM...SUNDAY NIGHT THROUGH FRIDAY...SNOW SHOWERS WILL LINGER 
ACROSS THE CENTRAL IDAHO MOUNTAINS AND WRN MAGIC VALLEY SUNDAY NIGHT 
BEFORE DRYING OUT ON MONDAY. THIS WILL TRANSITION TOWARD A PERIOD OF 
HIGH PRESSURE AS AN UPPER LEVEL RIDGE WILL BUILD OVER OREGON TUESDAY 
THROUGH THURSDAY. THE RIDGE WILL AMPLIFY OVER THE FORECAST AREA ON 
WEDNESDAY AND THURSDAY FOR PREDOMINANTLY DRY CONDITIONS /AND MINIMAL 
AFTERNOON MIXING/ THROUGH EARLY FRIDAY. THIS COULD BRING AN 
INVERSION TO THE LOW ELEVATION VALLEYS OVER THE HOLIDAY TRAVEL 
PERIOD FOR AIR QUALITY AND VISIBILITY IMPACTS. HAVE ADJUSTED THE 
FORECAST GRIDS TO REFLECT INVERTED TEMPERATURES BASED ON ELEVATION 
...ALONG WITH WEAK SOUTHEAST WINDS THROUGH THURSDAY NIGHT. MODELS ARE
IN REASONABLE AGREEMENT BRINGING THE NEXT PACIFIC TROUGH INTO THE 
AREA LATE FRIDAY OR SATURDAY.

&&

.AVIATION...MODERATE SE TO SW SURFACE WINDS /LOCAL GUSTS TO 40 KTS/ 
THROUGH TONIGHT WITH ADVANCING COLD FRONT. WINDS ALOFT WILL BE 
MODERATE TO STRONG SOUTHWESTERLY. RAIN AND SNOW SHOWERS WILL DEVELOP
ALONG A LINE FROM KBKE TO KBNO THROUGH 00Z AND WILL MOVE EAST THROUGH
THE NIGHT WITH DIMINISHING CIGS AND DETERIORATING CONDITIONS. EXPECT 
AREAS OF MVFR AND LOCAL IFR ACROSS SE OREGON THE REMAINDER OF THE 
AFTERNOON...AFTER 03Z FOR IDAHO. SNOW LEVELS APPROXIMATELY 3500 FT 
...WITH RAIN AND SNOW MIX ACROSS LOWER VALLEYS. 

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
OR...NONE.
&&

$$

WEATHER.GOV/BOISE

SHORT TERM...VM
LONG TERM....CD/LH
AVIATION.....CD